This invention relates generally to film compositions useful for extrusion coating applications, and more specifically to providing sealant layers for packaging applications.
There are many examples of polymer compositions useful for extrusion coating applications, including blends of linear low density polyethylene (LLDPE) with high pressure (free radical) low density polyethylene (LDPE). Extrusion coating is a means of coating a substrate with a particular polymer such that the substrate is providing functionality such as sealability to yet another substrate or to itself. Examples include juice packs, typically having an interior polymer extrusion coated onto a foil substrate where the polymer coating is then sealed (adhered) to itself. Extrusion coating is a very particular process where “neck-in” is important in forming the coating. “Neck-in” refers to the ability of the polymer formulation to retain its width, or its original dimensions after extrusion. Minimizing the “neck-in” allows for the polymer formulation to more effectively and uniformly coat the substrate.
For example, U.S. Pat. No. 5,587,247, the disclosure of which is incorporated herein by reference, discloses resin compositions for extrusion molding comprising a high pressure ethylene polymer having an endothermic peak in the range of 80°-120° C., an ethylene copolymer having an endothermic peak in the range of 118°-130° C. and an ethylene copolymer having, among other properties, no endothermic peak above 110 C.
However, there is still a need for a polymer formulation which reduces “neck-in” while maintaining good sealability.